The objective is to work out an improved system for the maintenance of catalogs of autosomal dominant, autosomal recessive and X-linked phenotypes in Man. These lists are intended to be exhaustive. Each entry insofar as is known refers to a single genetic locus. The entry consists of the preferred designation for the trait, a brief description of phenotype and all genetic characteristics and key references and particularly those with genetic information. The catalogs are maintained on the computer. Two classes of entries are maintained, those in which the particular mode of inheritance is quite certain and those in which it remains to be completely established (the latter being included for heuristic purposes). The catalogs are maintained by survey of the current periodical and monographic literature. The catalogs have usefulness in genetic counseling, differential diagnosis of genetic disorders and in the evaluation of progress in the field of human genetics.